/**
 * @param {character[]} s
 * @return {void} Do not return anything, modify s in-place instead.
 */
 var reverseString = function(s) {
  let left = 0
  let right = s.length - 1
  while(left < right){
    let t = s[left]
    s[left] = s[right]
    s[right] = t
    left++
    right--
  }
  return s
};